Attempts heretofore made in the commercial production of expandable pellets of styrene-polymers were fraught with serious disadvantages, limitations and costly operations. That was due to the need to avoid serious agglomeration of the polymer pellets during the impregnation operation and the difficulty of handling inert gases and feeding the liquid impregnant into a stirring autoclave and retaining its vapors and these gases against leakage.
The extensively long time required for feeding in the liquid impregnant and completing the impregnation very seriously limits production capacity with consequent increased cost. Moreover, that requires very special and costly stuffing-box construction and also highly expensive, relatively short-lived packings in the need to maintain pressure-tight operation around the stirrer shaft, result in further shortcomings, and increased production cost and capacity restriction.
The foregoing various difficulties, disavantages and shortcomings in the piror art are avoided by the process of the invention.